PURPOSE: To obtain a material for a letter having concealable data display surfaces consisting of two continuous surfaces of two sets in total provided to the inside and outside thereof and suitable for continuous printing by applying an adhesive to four peripheral sides of two continuous surfaces becoming uniting surfaces when a board surface is folded into a Z-shape.

CONSTITUTION: Board 1 is divided into data display surfaces A, B, C by folding lines 2 and an adhesive is applied to four peripheral sides of two continuous surfaces becoming uniting surfaces when the board 1 is folded into a Z-shape and the board 1 is folded into the Z-shape along the folding lines to bond adhesive layers 5, 6 to form a letter body. Whereupon, continuous display surfaces of two sets in total are obtained on the inside and outside of the board in a concealable manner. Since the tab parts of both end edges of the board remain to the last because of Z-folding, continuous treatment becomes possible without losing the hold applied to a machine. Since the surface of the board is continuously developed as one surface in an oblong shape without being divided finely, a wide layout becomes possible and variegated elaborate plans can be devised on a paper surface. Especially, since a display surface consisting of two continuous concealable surfaces of two sets can be formed, more variable data can be applied.